Drill bit and cast-in-situ bored pile construction method

The invention provides a drill bit and a cast-in-situ bored pile construction method. The drill bit comprises a main shaft, a first sleeve, a limiting component, a spring, a second sleeve, at least three soil cutting drill arms and a fishtail drill bit, wherein the first sleeve, the limiting component, the spring and the second sleeve are sequentially connected to the outer side of the main shaft in a sleeving mode. Wherein the first sleeve and the fishtail drill bit are fixedly connected with the same end of the main shaft; the limiting part is fixed on the main shaft in a position-adjustable manner; one end of the spring abuts against the limiting component, and the other end of the spring is connected with the second sleeve. The second sleeve can repeatedly slide along the axial direction of the main shaft; the first end of each soil cutting drill arm is hinged to the first sleeve, and the second end of each soil cutting drill arm is hinged to the second sleeve. Each soil cutting drill arm comprises an upp